Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$229.93	3.858%	$238.8007	$238.80	$238.80	$238.80
Purchase #2	$195.68	11.809%	$218.7879	$218.79	$218.80	$218.80
Purchase #3	$40.92	12.149%	$45.8914	$45.89	$45.90	$45.90
Purchase #4	$242.39	8.333%	$262.5884	$262.59	$262.60	$262.60
Purchase #5	$63.52	4.791%	$66.5632	$66.56	$66.55	$66.60
Purchase #6	$160.86	6.183%	$170.806	$170.81	$170.80	$170.80
Purchase #7	$169.90	5.218%	$178.7654	$178.77	$178.75	$178.80
7 purchase totals =	$1,103.20		$1,182.2030	$1,182.21	$1,182.20	$1,182.30